The invention relates to the general field of acoustic treatments and sound spatialization.
The invention relates more particularly to playing back a multichannel audio signal via a determined playback device that has a plurality of loudspeakers arranged at fixed locations of the playback device.
The invention applies in preferred but non-limiting manner to a playback device of the acoustic enclosure type, also known as a “baffle structure”. In known manner, such an acoustic enclosure is constituted by a single or one-piece structure incorporating the various loudspeakers that are used for playing back the audio signal (the loudspeakers are not separable from the enclosure). An example acoustic enclosure is in particular a soundbar in which the various loudspeakers are incorporated.
The present invention also presents a particular advantage when it is applied to a so-called “compact” acoustic enclosure or more generally to a compact playback device.
In known manner, a compact playback device is a device of dimensions that are small (in particular relative to the dimensions of the room or the hall in which the playback device is to be placed), and in which the loudspeakers are mounted relatively close to one another.
It should be observed that the device may be a one-piece device (such as an acoustic enclosure), or in a variant it may be made up of a plurality of elements, which elements are grouped together so as to form an assembly that is compact, each element being provided with one or more loudspeakers.
By way of illustration, the long dimension of a compact playback device generally does not exceed 2 meters, whereas the spacing between adjacent loudspeakers is less than 50 centimeters.
Various methods exist in the prior art seeking to optimize the playback of a multichannel audio signal via a playback device, while taking account of the physical limits of the playback device, in particular those that result from the distribution of the loudspeakers of the playback device in three-dimensional space.
An example of such a method is described in Document WO 2012/025580 with reference to a plurality of playback devices having a plurality of loudspeakers distributed at various locations in a room so as to cover an extended listening spatial zone (the listening zone models the positions of the listeners).
That method relies on spatially analyzing the multichannel audio signal that it is desired to play back, making it possible to extract and locate the sound objects of the audio signal that are situated inside a sound playback window defined from the physical positions of the loudspeakers of the playback device and of the extended listening zone.
The extracted sound objects are played back inside the sound playback window as a function of their locations within the window by performing first playback treatment. This first playback treatment may for example be wave field synthesis (WFS) treatment, which is itself known.
The other components of the multichannel audio signal are also played back within the sound playback window, in application of second playback treatment (such as for example an intensity panning effect).
Although Document WO 2012/025580 performs spatial analysis and playback of the multichannel audio signal while taking account of the distribution of the loudspeakers of the playback device, in particular by means of the concept of the sound playback window, it is nevertheless restricted to use with playback devices having loudspeakers that are spread throughout the room in which the signal is to be played back and for playback in an extended listening zone.
However Document WO 2012/025580 does not specifically address playing back a multichannel audio signal via a playback device that is compact.
However using a compact playback device presents certain constraints, in particular in terms of the dimensions of the listening zone that can be expected, and of the sound playback window associated with the physical arrangement of the loudspeakers on the playback device, which dimensions are generally smaller than with a playback device made up of a plurality of entities spread throughout the room or the hall in which the device is placed, as envisaged in Document WO 2012/025580.
There therefore exists a need for a method of playing back a multichannel audio signal that is particularly well adapted to playback devices that are compact, and in particular to compact acoustic enclosures, and that makes it possible to optimize the rendering of the audio signal while maintaining intelligibility and clarity for the components of the signal.